The present invention relates to "throw away" meltblown fibrous sorbent media of thermoplastic fibers and, in particular, to meltblown fibrous sorbent media of thermoplastic fibers which are especially suited for absorbing oil or water and other liquids and the method of making such sorbent media:
Fibrous sorbent media made of thermoplastic fibers are used for many clean up applications including but not limited to: cleaning up oil spills on water; cleaning machinery, engines and other equipment; cleaning up oil, water, grease or other liquids from floors and other surfaces; etc. Typically, these fibrous sorbent media are intended to be properly discarded after only one use or only a few uses.
Fibrous polypropylene sorbent media is particularly well suited for such tasks. For example, fibrous polypropylene sorbent media has an affinity for oil and is hydrophobic. Thus, fibrous polypropylene sorbent media will soak up or absorb oil without absorbing water and can be used effectively to clean up oil spills on water. When the fibers of fibrous polypropylene sorbent media are treated or coated with a surfactant, the media will absorb water and other similar liquids. Thus, when treated with a surfactant, fibrous polypropylene sorbent media can be used to clean up water and other liquids in addition to oil.
Previously, the process for producing the fibrous sorbent media manufactured and sold by Johns Manville International, Inc., has essentially included three processes. In the first process, a thin meltblown tightly bonded cover stock is formed having a basis weight of about 0.75 oz/yd.sup.2 or another cover stock, such as but not limited to a spun bond cover stock is formed. In the second process an air-laid, non-woven mat or fibrous layer of loose lofty randomly oriented meltblown thermoplastic fibers, e.g. polypropylene fibers having a mean diameter of about 15 microns, and of the required thickness is formed. In a third process a heated pin or calendar roll collates a layer of cover stock onto each major surface of the mat or fibrous layer and, through the heated pins of a pin or calendar roll, heat point bonds the layers of cover stock to the major surfaces of the mat. The resulting product is a fibrous sorbent media laminate with a fibrous core layer of loose lofty fibers encapsulated between two surface layers of cover stock that are heat point bonded to the fibrous core layer. The loose fibers within the media provide an effective surface area for good liquid absorption and the layers of cover stock provide the laminate with the required tensile strengths and abrasion resistance. The heat point bonding of the layers of cover stock to the fibrous core layer provides the fibrous sorbent media with added integrity and improves the "handle-ability" of the product. Fibrous thermoplastic sorbent media laminates, such as the sorbent media just described, provide good liquid absorption for many applications. However, since these sorbent media are primarily used for applications where the sorbent media is discarded after only one use or only a few uses, there has remained a need for fibrous thermoplastic sorbent media, with equal or better liquid absorption and abrasion resistance properties, that can be more economically produced.